Cheap, portable, optical scanner
 

I am interested in analyzing surfaces of objects
to detect natural and man-made shaping of the object surface,
and I have been experimenting,
using a MP3 player/recorder to record the sound,
as I drag various fabrics attached to the player across the objects.

Fingerprint scanners operated about 500 DPI,
and the "ridges" that I want to "transducer"
are a little coarser than that.

I have experimented with various "transducer interface materials"
glued onto the MP3 player, and I have not found a
suitable material, as all materials have many
resonances, and those, combined with the
resonances of the MP3 players I have used,
tend to obscure the data associated with the surfaces,
that I want to analyze.

I would appreciate any input and ideas about
producing an audio signal that models a surface,
in a small portable, inexpensive package.

A small, low-power, laser probe would probably do a better job,
and I am hopeful of using an MP3 player/recorder for this,
as the cost, size, power consumption and frequency response
seems to be ideal.

Does anyone have any input on how
an optical mouse might work as a surface scanner,
and how it can be interfaced to an MP3 player?

The data from the MP3 player would be downloaded into
a PC and analyzed. I have experimented with a number of
time series analyzer programs such as SigView,
and would also appreciate any suggestions on how to best present the data,
so it could be interpreted by a layman.

Thanks in advance for any help you can provide.

--
Tom Potter
http://home.earthlink.net/~tdp
http://photos.yahoo.com/tdp1001

I read in sci.electronics.design that Tom Potter
wrote (in ) about 'Cheap, portable,
optical scanner', on Sat, 19 Mar 2005:
I would appreciate any input and ideas about
producing an audio signal that models a surface, in a small portable,
inexpensive package.

A pickup cartridge for vinyl records is made for this job. You would
need an amplifier to connect it to the MP3 player.

There are two sorts of cartridge - piezo electric and magnetic. The
piezo type has an output proportional to stylus displacement, but the
sensitivity steps down from the low-frequency value at 500 Hz and below
to half that value at 2 kHz and above (roughly). The piezo type is a
capacitive source and requires an amplifier with a high resistive input
impedance.

The magnetic type has an output proportional to stylus speed, with the
above stepped response superimposed on that. It has an inductive and
resistive source impedance and requires a specific resistive load,
normally 47 kohms.
--
Regards, John Woodgate, OOO - Own Opinions Only.
There are two sides to every question, except
'What is a Moebius strip?'
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

I am interested in analyzing surfaces of objects
to detect natural and man-made shaping of the object surface,
and I have been experimenting,
using a MP3 player/recorder to record the sound,
as I drag various fabrics attached to the player across the objects.

Are you actually MP3-compressing the received data? I would be very
concerned that you're losing important information there. MP3 was
designed to reproduce audio, it wasn't designed as a general-purpose
compression algorithm for analog data capture sessions.

It sounds like each of these samples is probably not very large, can
you capture them without compression, i.e. as raw PCM data?

Tom Potter wrote:
I am interested in analyzing surfaces of objects
to detect natural and man-made shaping of the object surface,
and I have been experimenting,
using a MP3 player/recorder to record the sound,
as I drag various fabrics attached to the player across the objects.



Use a Webcam, and if necessary put a magnifying lens in front !
Why are you trying to build an ACOUSTIC Force Microscope to examine
Macroscopic Objects !

Yukio YANO

a retired Scanning Electron Microscope person.

"Tom Potter" wrote in message
...
I am interested in analyzing surfaces of objects
to detect natural and man-made shaping of the object surface,
and I have been experimenting,
SNIP

Maybe the reading head of a CD-player?

Wim

"John Woodgate" wrote in message
...
I read in sci.electronics.design that Tom Potter
wrote (in ) about 'Cheap, portable,
optical scanner', on Sat, 19 Mar 2005:
I would appreciate any input and ideas about
producing an audio signal that models a surface, in a small portable,
inexpensive package.

A pickup cartridge for vinyl records is made for this job. You would
need an amplifier to connect it to the MP3 player.

There are two sorts of cartridge - piezo electric and magnetic. The
piezo type has an output proportional to stylus displacement, but the
sensitivity steps down from the low-frequency value at 500 Hz and below
to half that value at 2 kHz and above (roughly). The piezo type is a
capacitive source and requires an amplifier with a high resistive input
impedance.

The magnetic type has an output proportional to stylus speed, with the
above stepped response superimposed on that. It has an inductive and
resistive source impedance and requires a specific resistive load,
normally 47 kohms.

Thanks for the input.

I will try this,
if I can't come up with a suitable optical device.

--
Tom Potter
http://home.earthlink.net/~tdp
http://photos.yahoo.com/tdp1001

wrote in message
oups.com...

I am interested in analyzing surfaces of objects
to detect natural and man-made shaping of the object surface,
and I have been experimenting,
using a MP3 player/recorder to record the sound,
as I drag various fabrics attached to the player across the objects.

Are you actually MP3-compressing the received data? I would be very
concerned that you're losing important information there. MP3 was
designed to reproduce audio, it wasn't designed as a general-purpose
compression algorithm for analog data capture sessions.

It sounds like each of these samples is probably not very large, can
you capture them without compression, i.e. as raw PCM data?

I am experimenting using the wave recording feature
of MP3 players, and this works okay,
except for the resonances in my MP3 player cases,
and in my "transducer interfaces".

As far as I know,
no MP3 player compresses the audio input.

In other words, they have an MP3 decoder,
but not an MP3 encoder on the chip.

But that said, it really doesn't matter if it
compressed to MP3 or not,
as lossy encoding won't affect my analysis much.

--
Tom Potter
http://home.earthlink.net/~tdp
http://photos.yahoo.com/tdp1001

"Yukio YANO" wrote in message
news:Q0__d.726621$8l.66584@pd7tw1no...
Tom Potter wrote:
I am interested in analyzing surfaces of objects
to detect natural and man-made shaping of the object surface,
and I have been experimenting,
using a MP3 player/recorder to record the sound,
as I drag various fabrics attached to the player across the objects.

Use a Webcam, and if necessary put a magnifying lens in front !
Why are you trying to build an ACOUSTIC Force Microscope to examine
Macroscopic Objects !

A webcam would generate too much data.

I need a small, cheap, low power, portable device
that can be plugged into a computer USB port.

( This is for a possible consumer product.)

--
Tom Potter
http://home.earthlink.net/~tdp
http://photos.yahoo.com/tdp1001

"Wim Ton" wrote in message
. uk...

"Tom Potter" wrote in message
...
I am interested in analyzing surfaces of objects
to detect natural and man-made shaping of the object surface,
and I have been experimenting,
SNIP

Maybe the reading head of a CD-player?

Sounds like a good idea!
Maybe I'll try this.

--
Tom Potter
http://home.earthlink.net/~tdp
http://photos.yahoo.com/tdp1001